Nectar robbery by a hermit hummingbird: association to floral phenotype and its influence on flowers and network structure
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Interactions between flowers and their visitors span the spectrum from mutualism to antagonism. The literature is rich in studies focusing on mutualism, but nectar robbery has mostly been investigated using phytocentric approaches focused on only a few plant species. To fill this gap, we studied the interactions between a nectar-robbing hermit hummingbird, Phaethornis ruber, and the array of flowers it visits. First, based on a literature review of the interactions involving P. ruber, we characterized the association of floral larceny to floral phenotype. We then experimentally examined the effects of nectar robbing on nectar standing crop and number of visits of the pollinators to the flowers of Canna paniculata. Finally, we asked whether the incorporation of illegitimate interactions into the analysis affects plant–hummingbird network structure. We identified 97 plant species visited by P. ruber and found that P. ruber engaged in floral larceny in almost 30 % of these species. Nectar robbery was especially common in flowers with longer corolla. In terms of the effect on C. paniculata, the depletion of nectar due to robbery by P. ruber was associated with decreased visitation rates of legitimate pollinators. At the community level, the inclusion of the illegitimate visits of P. ruber resulted in modifications of how modules within the network were organized, notably giving rise to a new module consisting of P. ruber and mostly robbed flowers. However, although illegitimate visits constituted approximately 9 % of all interactions in the network, changes in nestedness, modularity, and network-level specialization were minor. Our results indicate that although a flower robber may have a strong effect on the pollination of a particular plant species, the inclusion of its illegitimate interactions has limited capacity to change overall network structure.
KeywordsAntagonism Atlantic rainforest Modularity Mutualism Phaethornis ruber Plant–pollinator interactions
We thank the staff and administration of the Núcleo Picinguaba for the permission to carry out our study, Marcelo F. Moro for the map in the ESM, and Aline G. Coelho for sharing information on P. ruber robbing in flowers from her unpublished study. We are also grateful to the two anonymous reviewers and the editor for comments on a previous version of the manuscript. Financial support was provided by CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnológico) through a PhD scholarship to PKM and research grant to MS; CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) through a PDSE scholarship to PKM (processo: 99999.012341/2013-04) and JVB (processo: 99999.008012/2014-08) and a Ph.D. scholarship to JVB. PKM, JVB, and BD also thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate. The experiments in this study comply with the current laws of Brazil.
Conflict of interest
The authors declare that they have no conflict of interest.
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